Soil Science General Information PDF

Soils Ag Science Soil I. Soil is a layer on the earth’s crust that provides a combination of resources. Allow for the growth of plants and animals. A. Oxygen – needed for adequate root growth B. Temperature – soil absorbs heat from the...

Soils Ag Science Soil I. Soil is a layer on the earth’s crust that provides a combination of resources. Allow for the growth of plants and animals. A. Oxygen – needed for adequate root growth B. Temperature – soil absorbs heat from the sun. Used for plant growth and seed germination C. Water – used for plant growth D. Carbon – utilized in the form of organic matter E. Nutrients – provided as minerals. Broken down as nitrogen and recycled through decaying material. II. Soil is composed of 4 different components. A. Solid Portion (50%) 1. Mineral Matter – 45% of the soil. Partially decomposed rock, ie. sand, silt, clay 2. Organic Matter - ~5% of the soil. Partially decomposed plant & animal material. Gives soil its color B. Pore spaces (50% of the soil) 1. Air – accounts for 25% of the soil. When soils are wet, less air. When soils are dry, more air. 2. Water – accounts for 25% of the soil. When it rains, water either enters the soil or runs off. Water cont. Infiltration – process of water soaking into the soil. Once water is in the soil, the movement downward is called percolation. A soil that allows for both is called permeable  Water in the soil my be one of three types – Gravitational water – water that drains through the pore spaces (leaching occurs) – Capillary water – water that is held between particles of soil against forces of gravity; may move upward or sideways – Hygroscopic water – water that forms a thin film around individual soil particles; unavailable to plants. III. Abundant life can be found in soil. A. Forms of life in the soil include: 1. Earthworms 2. Insects 3. Bacteria 4. Fungi 5. Other organisms B. Bacteria & fungi have an important role in the soil. They breakdown o.m. and release nutrients C. Earworms, ants, crawfish, moles, and other organisms improve the tilth, or ease at which soil can be worked. These organisms create openings in the soil as they tunnel. This helps drainage and improves gas exchange. IV. Plants depend on soil to provide 4 basic needs. A. Anchorage – soil acts to provide a firm support as roots grow throughout the soil. B. Water – soil provides nearly all of the water used by plants. Water is absorbed through the plants’ roots. C. Oxygen – nearly all organisms need oxygen. Roots don’t have ample supplies, so they need good soil aeration to allow gas exchange. D. Nutrients – of the 16 nutrients considered to be essential for plant growth, 13 are obtained from the soil. Root hairs absorb the nutrients dissolved in soil water. V. Ag depends on soil to grow food, fiber, and other plants. A. Cropland – land on which soil is worked B. Grazing land – land used for grazing cattle and sheep; perennial forage. C. Forests – land used for growing trees, which is later harvested D. Water structures – ponds and other reservoirs are constructed out of soil. Non-ag uses of soil A. Recreation – playgrounds, sports fields, jogging paths, golf courses, parks, camp grounds,etc. B. Foundations – buildings depend on a solid soil base upon which a building is to be built and remain sound. C. Waste disposal – used for the treatment of human sanitary wastes. D. Building materials – build underground, into hillsides, adobe Five factors that affect soil formation A. Parent Material – type of rock that soil is made from. Igneous metamorphic sedimentary B. Climate – temperature & moisture C. Living organisms – organisms (bugs & worms) and plants in the soil. D. Topography – hills and valleys E. Time or weathering – age of the soil and climate Parent material is formed by the disintegration and decomposition of rock THE MAIN KINDS OF SOIL PARENT MATERIALS A. Most soils (in Illinois) were formed by 800px-Grosser_Aletschgletscher_3178 glaciers. Newer and more productive Older and less productive B. About 64% of the soil is formed from loess. Loess occurred from the blowing of the soil after the glaciers. C. About 7% of the state soil is due to recent stream deposits. This is referred to as alluvium. D. Bedrock – most of the shale, sandstone, or limestone bedrock (in Illinois) is buried by loess. Except in extreme NW and Southern Illinois.  Organic soils – less than 1% of the soils in Illinois are classified as organic. Occur where formerly shallow ponds or supported swamp vegetation. Wet conditions slow decay of organic materials. Peat exploitation in East Frisia, Germany – Two types: muck and peat Topography is the slope characteristics of land. How do living organisms affect the soil? Organisms living in the soil, like plants, insects and microbes actively affect soil formation.  Native Vegetation has the greatest affect on the development of soil – plants that once grew in it. Two primary types – Tall grass prairie – Deciduous hard wood forest A. Prairie soils have a dark and deep surface layer. The roots of the prairie grass filled the top of the soil. 2178136074 B. Timber soils tend to have a thin, moderately dark layer. Due to organic matter accumulating on the surface and decaying quickly.  The surface pattern on this pedestal rock is honeycomb weathering, caused by salt crystallisation. This example is at Yehliu, Taiwan. Weathering 1. Physical weathering 1. The affects of climatic factors such as temperature, water, and wind. Freezing and A rock in southern Iceland fragmented by freeze-thaw action thawing are a major contributor. Pressure Release of granite.  A freshly broken rock shows differential chemical weathering (probably mostly oxidation) progressing inward. This piece of sandstone was found in glacial drift near Angelica, New York Weathing (cont.) 2. Chemical weathering a. changes the chemical makeup of rock and breaks it down. Rainwater can dissolve minerals. b. Some minerals react with oxygen. Oxidation further decomposes rock. Weathering (cont.) B. Weathering causes soil to: 1. Develop 2. Mature 3. Age Climate Refers to rainfall, freezing, thawing, wind, 1956679431 and sunlight. 2388175119 341962552 49707169 604244132 Climate (cont) B. The climate (in Illinois) is said to be of the continental type. Hot Summers, Cold Winter Climate (cont.) C. Rainfall and Wind wear the rock away a little at a time. Physical Features of soil Soils have many features that are used to recognize the difference between them. They include: A. Texture – coarseness of fineness of soil particles B. Structure – the way in which soil particles are held together C. Depth of horizons – depth of each soil D. Color – darkness or lightness of soil color Colors A. Very Dark - ~5% O.M. B. Dark - ~ 3.5% O.M. C. Moderately Dark - ~ 2.5% O.M. D. Light - ~2% O.M. E. Very Light - ~1.5% O.M. Soil Texture A. Soil Texture is the fineness or coarseness of a soil. 1. Sand – largest particle 2. Silt – medium sized particle 3. Clay – small particle Clay Sand Silt  Patterns in the sand Quaternary clay in Estonia. silt deposits around house and car in New Orleans left by flooding from a breach in the London Avenue Canal  Texture (cont.) B. Texture is important because it affects: 1. Water holding capacity – the ability of a soil to retain water for use. 2. Permeability – ease with which air & water my pass through the soil. 3. Soil Workability – the ease with which soil may be tilled and amount of time after rain. 4. Ability for plants to grow, ie carrots Texture (cont.) A. Soil texture may be determined in 2 ways 1. Using a textural triangle. This is found be using the percentage of each type of soil particle. Textural Triangle Ribbon Method a. Fine textured b. Moderately fine textured c. Medium textured d. Moderately coarse e. Coarse  Ribbon testing Ball of clay made in fist Starting to form a ribbon Clay Ribbon (>2") Starting to make a ribbon from sand Ribbons are hard to form with sand (